Transaminase of branched chain amino acids. XI. Leucine (methionine) transaminase of rat liver mitochondria.

An aminotransferase (transaminase) which is active for leucine and methionine, but not for valine or isoleucine, was purified from rat liver mitochondria. The purified preparation appeared homogeneous on polyacrylamide disc gel electrophoresis. Its molecular weight was shown to be 55 000 by gel filtration. It differed from enzyme II (leucine aminotransferase, EC 2.6.1.6) in the supernatant fraction, another transaminase which is also specific for leucine and methionine, in molecular weight, Km values for substrates, electrophoretic mobility, chromatographic behavior and heat stability. From comparison with related transaminases it was concluded to be a new enzyme and named mitochondrial leucine (methionine) transaminase.